Bonded abrasive articles have abrasive particles bonded together by a bonding medium. Bonded abrasives include, for example, stones, hones, grinding wheels, and cut-off wheels. The bonding medium is typically an organic resin, but may also be an inorganic material such as a ceramic or glass (i.e., vitreous bonds).
Cut-off wheels are typically thin wheels used for general cutting operations. The wheels are typically about 20 to about 2500 millimeter in diameter, and from less than one millimeter (mm) to about 16 mm thick. Typically, the thickness is about one percent of the diameter. They are typically operated at speeds of from about 35 msec to 100 msec, and are used for operations such as cutting metal or stone; for example, to a nominal length. Cut-off wheels are also known as “abrasive cut-off saw blades” and, in some settings such as foundries, as “chop saws”. As their name implies, cut-off wheels are commonly used to cut stock (i.e., a workpiece) such as, for example, metal rods, by abrading through the stock.
Cut-off wheels can be used in dry cutting, wet-cutting, cold-cutting, and hot-cutting applications. During cutting heat generated by friction may cause physical changes in the material being cut; for example, carbon steel may develop a bluish color that may be undesirable for mechanical (e.g., blue brittleness) and/or aesthetic reasons.
When evaluating the cutting performance of abrasive wheels (e.g., grinding wheels and cut-off wheels), a ratio known as the G-ratio is commonly used. The G-ratio has been variously defined as: the grams of stock removed divided by the grams of wheel lost, volume of stock removed divided by the volume of wheel lost, and as the cross-sectional area of the cut formed in the stock divided by the area on the round side of the cut-off wheel that is lost. As used herein, the term “G-ratio” refers only to the latter definition (i.e., the cross-sectional area of the cut formed in the stock divided by the area on the round side of the cut-off wheel that is lost).